Morphology and metabolism of storage substances contribution to alkali stress responses in two contrasting barley cultivars during germination stage

Barley (Hordeum vulgare L.) is a globally significant crop and serves as a pioneer crop for improving saline-alkaline soils due to its salt-alkali tolerant properties. However, the response mechanism of barley to alkali stress remains unclear. In this study, two barley genotypes with contrasting performance under alkali stress were selected: the alkali-tolerant SCMS and the alkali-sensitive QT9919. The morphological and physiological mechanisms of these two barley cultivars in response to alkali stress were elucidated. Results showed that alkali stress inhibited germination in QT9919, leading to significant decreases in germination vigor, plant height and root length. On the other hand, SCMS presented stronger water absorbing capacity than QT9919 under all circumstances. Furthermore, starch degradation and sugar metabolism were suppressed by alkali stress in both barley cultivars through downregulation of genes expression and reduction of enzymes activities involved in the processes of EMP (Embden-Meyerhof-Parnas), tricarboxylic acid cycle (TCA), and pentose phosphate pathway (PPP). Notably, enzyme activity of hexokinase (HK) and malic dehydrogenase (MDH) showed significant changes under alkali stress between the two barley genotypes. This study provides insights into screening barley germplasm with strong alkali-tolerance and holds significant implications for improving and utilizing of saline-alkaline soils.